Liquid crystal composition and liquid crystal display element

ABSTRACT

An advantage of the present invention is to provide a liquid crystal composition, which satisfies two or more of characteristics such as a wide nematic phase temperature range, a small viscosity, a suitable optical anisotropy, a large negative dielectric anisotropy, and a large specific resistance. One aspect of the invention is to provide a liquid crystal composition having properly balanced characteristics. Another aspect of the invention is to provide a liquid crystal display element, which includes such a composition to have a large voltage holding ratio. A further aspect of the invention is to provide an AM element, which includes a composition having characteristics such as a small viscosity, an optical anisotropy of 0.05 to 0.11, and a dielectric anisotropy of −6.5 to −2.0, and is suitable for a VA mode, an IPS mode, etc. 
 
A liquid crystal composition with a negative dielectric anisotropy, comprising at least one compound selected from the group of compounds represented by the following formula (1) as a first component, and at least one compound selected from the group of compounds represented by the following formulas (2-1) to (2-3) and (3-1) to (3-4) as a second component:  
                 
 
wherein R 1  is alkyl or alkenyl; R 2 is alkyl, alkenyl, or alkoxy; R 3  is alkyl, alkenyl, alkoxy, or —COO—R 4 , in which R 4  is alkyl; R 5  is alkyl, alkenyl, alkoxy, or alkoxymethyl; Z 1  and Z 2  are independently a single bond, —CH 2 O—, —OCH 2 —, —(CH 2 ) 2 —, —(CH 2 ) 4 —, —CF 2 O—, —OCF 2 —, —C 2 H 4 CF 2 O—, —C 2 H 4 OCF 2 —, —CF 2 OC 2 H 4 —, or —OCF 2 C 2 H 4 —, Z 3  is a single bond or —COO—; A 1  is 1,4-cyclohexylene or 1,4-phenylene; A 2  and A 3  are independently 1,4-cyclohexylene, 1,4-phenylene, 1,4-phenylene in which any hydrogen may be replaced by fluorine, or 2-difluoromethyl-3-fluoro-1,4-phenylene; A 4  is 1,4-cyclohexylene, 1,4-phenylene, or 1,4-phenylene in which a hydrogen is replaced by a fluorine; A 5  is 1,4-phenylene or 1,4-phenylene in which a hydrogen is replaced by a fluorine; A 6 is 2-fluoro-1,4-phenylene; n is 0 or 1; in the formula (1), when n is 0, A 2  is 2-difluoromethyl-3-fluoro-1,4-phenylene, and Z 2  is a single bond; and in the formula (1), when n is 1, one of A 2  and A 3  is 2-difluoromethyl-3-fluoro-1,4-phenylene, and one of Z 1  and Z 2  is a single bond.

BACKGROUND OF THE INVENTION

1. Filed of the Invention

The present invention relates mainly to a liquid crystal compositionsuitable for active matrix (AM) elements, and an AM element includingthe composition.

2. Related Art

Liquid crystal display elements are classified by liquid crystaloperating modes into phase change (PC), twisted nematic (TN), supertwisted nematic (STN), electrically controlled birefringence (ECB),optically compensated bend (OCB), in-plane switching (IPS), and verticalalignment (VA) elements, and so forth. The liquid crystal displayelements are classified also by driving modes into passive matrix (PM)and active matrix (AM) elements. The PM elements are further classifiedinto static and multiplex elements, and so forth, and the AM elementsare further classified into thin film transistor (TFT) and metalinsulator metal (MIM) elements, and so forth. The TFTs are classifiedinto amorphous silicons, polycrystal silicons, and continuous grainsilicons, and the polycrystal silicons are further classified byproduction processes into high temperature type silicons and lowtemperature type silicons. Further, the liquid crystal display elementsare classified based on light sources into reflection type elementsutilizing a natural light, transmission type elements utilizing abacklight, and semi-transmission type elements utilizing both thenatural light and the backlight.

These elements include a liquid crystal composition having suitablecharacteristics. The general characteristics of the composition shouldbe improved to obtain an AM element having excellent generalcharacteristics. Table 1 below summarizes relationships of the generalcharacteristics between the composition and the AM element. The generalcharacteristics of the composition will be explained further in terms ofa commercially available AM element. The nematic phase temperature rangeof the composition relates to the temperature range in which the elementcan be used. The higher limit temperature of the nematic phasetemperature range is preferably 70° C. or more, and the lower limittemperature is preferably −20° C. or less. The viscosity of thecomposition relates to the response time of the element. It is preferredthat the element has a short response time to display a moving image.Accordingly, the composition preferably has a small viscosity, and morepreferably has a small viscosity at a low temperature. TABLE 1 Generalcharacteristics of a liquid crystal composition and an AM elementGeneral characteristics of a General characteristics of No compositionan AM Element 1 Temperature range of a Usable temperature range isnematic phase is wide wide 2 Viscosity is small¹⁾ Response time is short3 Optical anisotropy is Contrast ratio is large suitable 4 Thresholdvoltage is low Electric power consumption is small and a contrast ratiois large 5 Specific resistance is large Voltage holding ratio is smalland a contrast ratio is large¹⁾A liquid crystal composition can be injected into a cell in a shorttime.

The optical anisotropy of the composition relates to the contrast ratioof the element. An element of a VA or IPS mode, etc. utilizes anelectrically controlled birefringence. Thus, to maximize the contrastratio of the VA mode element, a product (Δn·d) of the optical anisotropy(Δn) of the composition and the cell gap (d) of the element is designedto be uniform. For example, the product is 0.30 to 0.35 μm in the VAmode and 0.20 to 0.30 μm in the IPS mode. The cell gap (d) is generally3 to 6 μm, so that the optical anisotropy of the composition isgenerally within the range of 0.05 to 0.11. A large dielectricanisotropy of the composition contributes to a small driving voltage ofthe element. Thus, the composition preferably has a large dielectricanisotropy. A composition having a positive dielectric anisotropy isused for common AM elements, while a composition having a negativedielectric anisotropy is used for VA-mode AM elements. A large specificresistance of the composition contributes to a large voltage holdingratio and a large contrast ratio of the element. Accordingly, thecomposition preferably has a large specific resistance initially, andfurther preferably has a large specific resistance even after it hasbeen used for a long time.

A composition having a negative dielectric anisotropy contains acompound having a negative dielectric anisotropy. For example, as such acompound, a 2-difluoromethyl-3-fluoro-1,4-phenylene-containing compoundhaving a negative dielectric anisotropy is described in Patent Document1, etc.

-   Patent Document 1: WO 2000-39063 A (U.S. Pat. No. 6,576,303 B1)

SUMMARY OF THE INVENTION

The present invention has a liquid crystal composition with a negativedielectric anisotropy, comprising at least one compound selected fromthe group of compounds represented by the following formula (1) as afirst component, and at least one compound selected from the group ofcompounds represented by the following formulas (2-1) to (2-3) and (3-1)to (3-4) as a second component:

wherein R¹ is alkyl or alkenyl; R² is alkyl, alkenyl, or alkoxy; R³ isalkyl, alkenyl, alkoxy, or —COO—R⁴, in which R⁴ is alkyl; R⁵ is alkyl,alkenyl, alkoxy, or alkoxymethyl; Z¹ and Z² are independently a singlebond, —CH₂O—, —OCH₂—, —(CH₂)₂—, —(CH₂)₄—, —CF₂O—, —OCF₂—, —C₂H₄CF₂O—,—C₂H₄OCF₂—, —CF₂OC₂H₄—, or —OCF₂C₂H₄—; Z³ is a single bond or —COO—; A¹is 1,4-cyclohexylene or 1,4-phenylene; A² and A³ are independently1,4-cyclohexylene, 1,4-phenylene, 1,4-phenylene in which a hydrogen isreplaced by a fluorine, or 2-difluoromethyl-3-fluoro-1,4-phenylene; A⁴is 1,4-cyclohexylene, 1,4-phenylene, or 1,4-phenylene in which ahydrogen is replaced by a fluorine; A⁵ is 1,4-phenylene or 1,4-phenylenein which a hydrogen is replaced by a fluorine; A⁶ is2-fluoro-1,4-phenylene; n is 0 or 1; in the formula (1), when n is 0, A²is 2-difluoromethyl-3-fluoro-1,4-phenylene, and Z² is a single bond; andin the formula (1), when n is 1, one of A² and A³ is2-difluoromethyl-3-fluoro-1,4-phenylene, and one of Z¹ and Z² is asingle bond.

The present invention also has a liquid crystal display elementincluding the liquid crystal composition described above.

DETAILED DESCRIPTION

Terms used in the specification and claims are defined as follows: Theliquid crystal composition of the present invention and the liquidcrystal display element of the invention may occasionally be abbreviatedas the composition and the element, respectively. The term “a liquidcrystal display element” is a general term for a liquid crystal displaypanel and a liquid crystal display module. An element driven by anactive matrix may be abbreviated as an AM element, an element of a TNmode may be abbreviated as a TN element, and elements of other modes mayalso be abbreviated in the same manner. The liquid crystal compositionincludes a liquid crystalline compound. The term “a liquid crystallinecompound” is a general term for a compound having a liquid crystal phasesuch as a nematic phase and a smectic phase, and a compound having noliquid crystal phase and being useful as a component of the composition.The formulas (1) to (1-12) may be collectively abbreviated as theformula (1), and other formulas may be also abbreviated in the samemanner. At least one compound selected from a group of compoundsrepresented by the formula (1-1) may be abbreviated as a compound (1-1),and compounds represented by other formulas may also be abbreviated inthe same manner.

A higher limit temperature of a nematic phase temperature range may beabbreviated as a higher limit temperature. A lower limit temperature ofa nematic phase temperature range may be abbreviated as a lower limittemperature. The term “a composition has a large specific resistance”means that the composition has a large specific resistance at theinitial stage and has a large specific resistance even after it has beenused for a long time. The term “an element has a large voltage holdingratio” means that the element has a large voltage holding ratio at theinitial stage and has a large voltage holding ratio even after it hasbeen used for a long time. Characteristics such as optical anisotropyare explained using values measured by methods described in Examples.The content (percentage) of each component of a composition is describedin percentage by weight (% by weight) based on the total weight of thecomposition.

An advantage of the present invention is to provide a liquid crystalcomposition, which satisfies two or more of characteristics such as awide nematic phase temperature range, a small viscosity, a suitableoptical anisotropy, a large negative dielectric anisotropy, and a largespecific resistance. One aspect of the invention is to provide a liquidcrystal composition having properly balanced characteristics. Anotheraspect of the invention is to provide a liquid crystal display element,which includes such a composition to have a large voltage holding ratio.A further aspect of the invention is to provide an AM element, whichincludes a composition having characteristics such as a small viscosity,an optical anisotropy of 0.05 to 0.11, and a dielectric anisotropy of−6.5 to −2.0, and is suitable for a VA mode, an IPS mode, etc.

The present invention has the following.

1. A liquid crystal composition with a negative dielectric anisotropy,comprising at least one compound selected from the group of compoundsrepresented by the following formula (1) as a first component, and atleast one compound selected from the group of compounds represented bythe following formulas (2-1) to (2-3) and (3-1) to (3-4) as a secondcomponent:

wherein R¹ is alkyl or alkenyl; R²is alkyl, alkenyl, or alkoxy; R³ isalkyl, alkenyl, alkoxy, or —COO—R⁴, in which R⁴ is alkyl; R⁵ is alkyl,alkenyl, alkoxy, or alkoxymethyl; Z¹ and Z² are independently a singlebond, —CH₂O—, —OCH₂—, —(CH₂)₂—, —(CH₂)₄—, —CF₂O—, —OCF₂—, —C₂H₄CF₂O—,—C₂H₄OCF₂—, —CF₂OC₂H₄—, or —OCF₂C₂H₄; Z³ is a single bond or —COO—; A¹is 1,4-cyclohexylene or 1,4-phenylene; A² and A³ are independently1,4-cyclohexylene, 1,4-phenylene, 1,4-phenylene in which any hydrogenmay be replaced by fluorine, or 2-difluoromethyl-3-fluoro-1,4-phenylene;A⁴ is 1,4-cyclohexylene, 1,4-phenylene, or 1,4-phenylene in which ahydrogen is replaced by a fluorine; A⁵ is 1,4-phenylene or 1,4-phenylenein which a hydrogen is replaced by a fluorine; A⁶ is2-fluoro-1,4-phenylene; n is 0 or 1; in the formula (1), when n is 0, A²is 2-difluoromethyl-3-fluoro-1,4-phenylene, and Z² is a single bond; andin the formula (1), when n is 1, one of A² and A³ is2-difluoromethyl-3-fluoro-1,4-phenylene, and one of Z¹ and Z² is asingle bond.

2. The liquid crystal composition according to item 1, wherein, in theformula (1), Z¹ is a single bond, A¹ is 1,4-cyclohexylene, A² is2-difluoromethyl-3-fluoro-1,4-phenylene, and n is 0.

3. The liquid crystal composition according to item 1, wherein, in theformula (1), Z¹ is a single bond or —CH₂O—, A¹ and A² are1,4-cyclohexylene, and A³ is 2-difluoromethyl-3-fluoro-1,4-phenylene.

4. The liquid crystal composition according to item 1, wherein the firstcomponent is at least one compound selected from the group of compoundsrepresented by the following formulas (1-1) to (1-12):R¹-A¹-Z⁴-A⁷-(A⁸)_(n)-R²   (1-1)R¹-A¹-Z⁵-A⁷-(A⁸)_(n)-R²   (1-2)R¹-A¹-Z⁶-A⁷-(A⁸)_(n)-R²   (1-3)R¹-A¹-Z⁴-A⁸-A⁷-R²   (1-4)R¹-A¹-Z⁵-A⁸-A⁷-R²   (1-5)R¹-A¹-Z⁶-A⁸-A⁷-R²   (1-6)R¹-A¹-A⁸-Z⁴-A⁷-R²   (1-7)R¹-A¹-A⁸-Z⁵-A⁷-R²   (1-8)R¹-A¹-A⁸-Z⁶-A⁷-R²   (1-9)R¹-A¹-A⁷-Z⁴-A⁸-R²   (1-10)R¹-A¹-A⁷-Z⁵-A⁸-R²   (1-11)R¹-A¹-A⁷-Z⁶-A⁸-R²   (1-12)wherein R¹ is alkyl or alkenyl; R² is alkyl, alkenyl, or alkoxy; Z⁴ is asingle bond, —CH₂O—, or —OCH₂—; Z⁵ is —(CH₂)₂— or —(CH₂)₄—; Z⁶ is—CF₂O—, —OCF₂—, —C₂H₄CF₂O—, —C₂H₄OCF₂—, —CF₂OC₂H₄—, or —OCF₂C₂H₄—; A¹ is1,4-cyclohexylene or 1,4-phenylene; A⁷ is 1,4-phenylene in which ahydrogen is replaced by a fluorine, or2-difluoromethyl-3-fluoro-1,4-phenylene; A⁸ is 1,4-cyclohexylene,1,4-phenylene, 1,4-phenylene in which a hydrogen is replaced by afluorine, or 2-difluoromethyl-3-fluoro-1,4-phenylene; one of A⁷ and A⁸is 2-difluoromethyl-3-fluoro-1,4-phenylene; n is 0 or 1; and in theformulas (1-1) to (1-3), when n is 0, A⁷ is2-difluoromethyl-3-fluoro-1,4-phenylene.

5. The liquid crystal composition according to item 4, wherein the firstcomponent is at least one compound selected from the group of thecompounds represented by the formulas (1-1), (1-3), (1-4), (1-6), (1-7),(1-9), (1-10), and (1-12).

6. The liquid crystal composition according to item 4, wherein, in theformula (1-1), Z⁴ is a single bond, A¹ is 1,4-cyclohexylene, A⁷ is2-difluoromethyl-3-fluoro-1,4-phenylene, and n is 0.

7. The liquid crystal composition according to item 4, wherein, in theformulas (1-4), (1-7), and (1-10), Z⁴ is a single bond or —CH₂O—, A¹ andA⁸ are 1,4-cyclohexylene, and A⁷ is2-difluoromethyl-3-fluoro-1,4-phenylene.

8. The liquid crystal composition according to any one of items 1 to 7,wherein the second component is at least one compound selected from thegroup of the compounds represented by the formulas (2-1) to (2-3).

9. The liquid crystal composition according to any one of items 1 to 7,wherein the second component is at least one compound selected from thegroup of the compounds represented by the formula (2-1).

10. The liquid crystal composition according to any one of items 1 to 7,wherein the second component is at least one compound selected from thegroup of the compounds represented by the formula (2-2).

11. The liquid crystal composition according to any one of items 1 to 7,wherein the second component is at least one compound selected from thegroup of the compounds represented by the formula (2-3).

12. The liquid crystal composition according to any one of items 1 to 7,wherein the second component is at least one compound selected from thegroup of the compounds represented by the formulas (3-1) to (3-4).

13. The liquid crystal composition according to any one of items 1 to 7,wherein the second component is at least one compound selected from thegroup of compounds represented by the following formulas (2-1-1),(2-1-2), (2-1-3), (2-1-4), (2-1-5), (2-2-1), (2-2-2), (2-3-1), (2-3-2),(2-3-3), and (2-3-4):

wherein R¹ is alkyl or alkenyl; R² is alkyl, alkenyl, or alkoxy; R⁴ isalkyl; and R⁵ is alkyl, alkenyl, alkoxy, or alkoxymethyl.

14. The liquid crystal composition according to item 13, wherein thesecond component is a compound selected from the group of the compoundsrepresented by the formulas (2-1-1), (2-1-4), (2-2-1), and (2-3-1).

15. The liquid crystal composition according to any one of items 1 to14, wherein the liquid crystal composition comprises 5 to 90% by weightof the first component and 5 to 90% by weight of the second componentbased on the total weight of the composition.

16. The liquid crystal composition according to any one of items 1 to15, further comprising at least one compound selected from the group ofcompounds represented by the following formula (4) as a third component:

wherein R¹ is alkyl or alkenyl; R² is alkyl, alkenyl, or alkoxy; Z⁴ andZ⁵ are independently —CF₂O— or —OCF₂—; A⁴ is 1,4-cyclohexylene,1,4-phenylene, or 1,4-phenylene in which a hydrogen is replaced by afluorine; and n is 0 or 1.

17. The liquid crystal composition according to item 16, wherein theliquid crystal composition comprises 2 to 50% by weight of the thirdcomponent based on the total weight of the composition.

18. The liquid crystal composition according to any one of items 1 to17, wherein the liquid crystal composition has a dielectric anisotropyof −6.5 to −2.0.

19. A liquid crystal display element comprising the liquid crystalcomposition according to any one of items 1 to 18.

20. The liquid crystal display element according to item 19, wherein theliquid crystal display element uses a VA or IPS mode, and is driven byan active matrix.

21. A method of using the liquid crystal composition according to anyone of items 1 to 18 for a liquid crystal display element that uses a VAor IPS mode and is driven by an active matrix.

The composition of the present invention satisfies two or more ofcharacteristics such as a wide nematic phase temperature range, a smallviscosity, a suitable optical anisotropy, a large negative dielectricanisotropy, and a large specific resistance. The liquid crystalcomposition has properly balanced characteristics. The element of theinvention includes the composition, and has a large voltage holdingratio. The element is suitable for an AM element using a VA mode, an IPSmode, etc. because it includes a composition having characteristics suchas a small viscosity, an optical anisotropy of 0.05 to 0.11, and adielectric anisotropy of −6.5 to −2.0.

The composition of the invention will be explained in the followingorder. First, the constitution of components in the composition will beexplained. Second, the main characteristics of the component compoundsand the main effects of the compounds on the composition will beexplained. Third, a suitable ratio of the component compounds and itsbasis will be explained. Fourth, a desirable embodiment of the componentcompounds will be explained. Fifth, concrete examples of the componentcompounds will be shown. Last, the synthesis methods of the componentcompounds will be explained.

First, the constitution of components in the composition will beexplained. There are 44 combinations of the compounds (1) to (4). Thecombinations are summarized in Tables 2 to 5 as Types 1 to 44. In Tables2 to 5, each circle means that the corresponding compound is used as acomponent of the composition, and each blank means that thecorresponding compound is not used as a component. For example, in thecase of Type 1, the compounds (1) and (2-1) are used as componentscontained in the composition. TABLE 2 Combination examples of compounds(1) Compound Compound Compound Compound (1) (2-1) (2-2) (2-3) Type 1 O OType 2 O O Type 3 O O Type 4 O O O Type 5 O O O Type 6 O O O Type 7 O OO O

TABLE 3 Combination examples of compounds (2) Compound Compound CompoundCompound Compound (1) (2-1) (2-2) (2-3) (4) Type 8 O O O Type 9 O O OType 10 O O O Type 11 O O O O Type 12 O O O O Type 13 O O O O Type 14 OO O O O

TABLE 4 Combination examples of compounds (3) Compound Compound CompoundCompound Compound (1) (3-1) (3-2) (3-3) (3-4) Type 15 O O Type 16 O OType 17 O O Type 18 O O Type 19 O O O Type 20 O O O Type 21 O O O Type22 O O O Type 23 O O O Type 24 O O O Type 25 O O O O Type 26 O O O OType 27 O O O O Type 28 O O O O Type 29 O O O O O

TABLE 5 Combination examples of compounds (4) Compound Compound CompoundCompound Compound Compound (1) (3-1) (3-2) (3-3) (3-4) (4) Type 30 O O OType 31 O O O Type 32 O O O Type 33 O O O Type 34 O O O O Type 35 O O OO Type 36 O O O O Type 37 O O O O Type 38 O O O O Type 39 O O O O Type40 O O O O O Type 41 O O O O O Type 42 O O O O O Type 43 O O O O O Type44 O O O O O O

At least one compound selected from the compounds (1-1) to (1-12) isused as the first component. In this case, the term “the compound (1-1)”means a single compound or a plurality of compounds, and this rule isapplicable to the compounds represented by other formulas. Preferredfirst components include the compounds (1-1), (1-3), (1-4), (1-6),(1-7), (1-9), (1-10), and (1-12). At least one compound selected fromthe group of the compounds (2-1) to (2-3) and (3-1) to (3-4) is used asthe second component. Preferred second components include the compounds(2-1), (2-2), and (2-3).

The composition of the invention is classified into a composition A or acomposition B. The composition A may further include another compoundsuch as a liquid crystalline compound, an additive, and an impurity.This liquid crystalline compound is different from the compounds (1) to(3). The liquid crystalline compound is added to the composition tocontrol the characteristics. Examples of the additives include opticallyactive compounds, coloring matters, ultraviolet absorbers, andantioxidants. The optically active compound is added to the compositionto induce a helical liquid crystal structure, thereby providing a twistangle. The coloring matter is added to the composition to adapt thecomposition to an element of a guest host (GH) mode. The impurity is acompound mixed in a process such as synthesis of each component andpreparation of the composition, and so forth.

The composition B essentially consists of the compounds selected fromthe compounds (1) to (3). The term “essentially” means that thecomposition B does not include a liquid crystalline compound other thanthe compounds (1) to (3), may further include an additive, an impurity,and so forth, and may further include a compound contained therein suchas an impurity, an optically active compound, a coloring matter, anultraviolet absorber, and an antioxidant. The composition B includesfewer components in comparison with the composition A. The composition Bis preferable to the composition A from the viewpoint of costs. Thecomposition A is preferable to the composition B because the physicalproperties of the composition can be further improved by mixing anotherliquid crystalline compound.

Examples of the ultraviolet absorbers include benzophenones, benzoates,and triazoles. Specific examples of the benzophenones include2-hydroxy-4-octoxybenzophenone. Specific examples of the benzoatesinclude 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate.Specific examples of the triazoles include2-(2-hydroxy-5-methylphenyl)benzotriazole,2-[2-hydroxy-3-(3,4,5,6-tetrahydroxyphthalimidomethyl)-5-methylphenyl]benzotriazole,and 2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole.

Examples of the antioxidants include phenols and organic sulfurcompounds. Specific examples of the phenols include3,5-di-tert-butyl-4-hydroxytoluene, 2,2′-methylenebis(6-tert-butyl-4-methylphenol), 4,4′-butylidenebis(6-tert-butyl-3-methylphenol),2,6-di-tert-butyl-4-(2-octadecyloxycarbonyl)ethylphenol, andpentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Specificexamples of the organic sulfur compounds include dilauryl3,3′-thiopropionate, dimyristyl 3,3′-thiopropionate, distearyl3,3′-thiopropionate, pentaerythritol tetrakis(3-laurylthiopropionate),and 2-mercaptobenzimidazole.

It is preferred that the additive such as the ultraviolet absorber andthe antioxidant is used in a large amount to attain the purpose.However, an excessively large amount of the additive is not preferred inview of the general characteristics of the composition. Though a largeamount of the antioxidant can prevent reduction of the specificresistance in the step of heating the composition, an excessively largeamount of the antioxidant is likely to reduce the higher limittemperature of the composition. For example, the content of theultraviolet absorber or the antioxidant may be 10 to 500 ppm based onthe total weight of the composition. The content is preferably 30 to 300ppm, more preferably 40 to 200 ppm.

Second, the main characteristics of the component compounds and the maineffects of the compounds on the composition will be explained. The maincharacteristics of the compounds are summarized in Tables 6 and 7. InTables 6 and 7, L means large or high, M means middle, and S means smallor low. The numbers 0 mean that the dielectric anisotropy is nearly zeroor very small. The letters L, M, and S are relative evaluation resultsin these compounds. TABLE 6 Characteristics of compounds (1) (1) (1) n =0 n = 1 (2-1) (2-2) (2-3) Higher limit S M S M L temperature Viscosity ML S S M Optical M M S-M M M-L anisotropy Dielectric M¹⁾ L¹⁾ O O Oanisotropy Specific L L L L L resistance¹⁾The compound has a negative dielectric anisotropy.

TABLE 7 Characteristics of compounds (2) (3-3) (3-3) (4) (4) (3-1) (3-2)n = 0 n = 1 (3-4) n = 0 n = 1 Higher limit S L S M-L M S M-L temperatureViscosity M M M M-L M M M-L Optical M M-L M L M M M-L anisotropyDielectric S¹⁾ S¹⁾ S¹⁾ S-M¹⁾ S¹⁾ M¹⁾ L¹⁾ anisotropy Specific L L L L L LL resistance¹⁾The compound has a negative dielectric anisotropy.

Third, a suitable ratio of the components and its basis will beexplained. The first component is the compound (1). The content of thefirst component is preferably at least 5% in view of negativelyincreasing the dielectric anisotropy or decreasing the thresholdvoltage, and is preferably at most 90% in view of decreasing the lowerlimit temperature. The content of the first component is more preferably30 to 85%. The second component is one of the compounds (2) and (3).When the second component is the compound (2), the content of the secondcomponent is preferably at least 5% in view of decreasing the viscosity,and is preferably at most 90% in view of negatively increasing thedielectric anisotropy or decreasing the threshold voltage. The contentof the compound (2) is more preferably 5 to 40%. When the secondcomponent is the compound (3), the content of the second component ispreferably at least 5% in view of negatively increasing the dielectricanisotropy or decreasing the threshold voltage, and is preferably atmost 90% in view of decreasing the lower limit temperature. The contentof the compound (3) is more preferably 30 to 85%. The composition mayinclude the compound (4) as the third component in addition to the firstand second components. In a case where the composition includes thethird component, the content of the third component is preferably atleast 2% in view of negatively increasing the dielectric anisotropy ordecreasing the threshold voltage, and is preferably at most 50% in viewof decreasing the lower limit temperature. The content of the thirdcomponent is more preferably 20 to 45%.

Fourth, a desirable embodiment of the component compounds will beexplained. The symbol R¹ is used in a plurality of the formulas for thecomponent compounds. R¹'s in the formulas may represent the same ordifferent ones in these compounds. For example, there is a case that R¹of the compound (1-1) is alkyl and R¹ of the compound (2-1) is alkenyl.This rule is also applicable to R², R³, R⁴, R⁵, A¹, A², A³, A⁴, A⁵, A⁶,Z¹, Z², Z³, Z⁴, and n.

R¹ is preferably alkyl having 1 to 10 carbon atoms or alkenyl having 2to 10 carbon atoms. R² is preferably alkyl having 1 to 10 carbon atoms,alkenyl having 2 to 10 carbon atoms, or alkoxy having 1 to 10 carbonatoms. R³ is preferably alkyl having 1 to 10 carbon atoms, alkenylhaving 2 to 10 carbon atoms, alkoxy having 1 to 10 carbon atoms, or—COO—R⁴, in which R⁴ is preferably alkyl having 1 to 10 carbon atoms. R⁵is preferably alkyl having 1 to 10 carbon atoms, alkenyl having 2 to 10carbon atoms, alkoxy having 1 to 10 carbon atoms, or alkoxymethyl having2 to 10 carbon atoms.

Preferred alkyl includes methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, and octyl, and more preferred alkyl includes ethyl, propyl,butyl, pentyl, and heptyl.

Preferred alkenyl includes vinyl, 1-propenyl, 2-propenyl, 1-butenyl,2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, and 5-hexenyl, and morepreferred alkenyl includes vinyl, 1-propenyl, 3-butenyl, and 3-pentenyl.A desirable —CH═CH— configuration of the alkenyl depends on the positionof the double bond. Trans configuration is desirable in 1-propenyl,1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl, 3-hexenyl, etc. Cisconfiguration is desirable in 2-butenyl, 2-pentenyl, 2-hexenyl, etc.

Preferred alkoxy includes methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy, and heptyloxy, more preferred alkoxy includes methoxy andethoxy.

Preferred alkoxymethyl includes methoxymethyl, ethoxymethyl,propoxymethyl, butoxymethyl, and pentyloxymethyl, more preferredalkoxymethyl includes methoxymethyl.

The —COO—R⁴ group is preferably methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, or butoxycarbonyl, more preferably methoxycarbonyl.

In the 1,4-cyclohexylene of the component compounds, trans configurationis preferable to cis configuration. The “1,4-phenylene in which ahydrogen is replaced by a fluorine” of A², A³, A⁴, A⁵, A⁷, or A⁸ is2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene,2,5-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene,2,3,5-trifluoro-1,4-phenylene, or 2,3,5,6-tetra-1,4-phenylene. A², A³,A⁴, and A⁵ are preferably 1,4-phenylene, 2-fluoro-1,4-phenylene,2,3-difluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene, or2,6-difluoro-1,4-phenylene, more preferably 2-fluoro-1,4-phenylene,2,3-difluoro-1,4-phenylene, or 2,6-difluoro-1,4-phenylene, respectively.3-fluoro-1,4-phenylene is equal to 2-fluoro-1,4-phenylene, and therebyis not described. This rule is applicable to the relation between2,5-difluoro-1,4-phenylene and 3,6-difluoro-1,4-phenylene, the relationbetween 2-difluoromethyl-3-fluoro-1,4-phenylene and3-difluoromethyl-2-fluoro-1,4-phenylene, etc. The compound (1) has2-difluoromethyl-3-fluoro-1,4-phenylene.

Z¹ and Z² are independently a single bond, —CH₂O—, —OCH₂—, —(CH₂)₂—,—(CH₂)₄—, —CF₂O—, —OCF₂—, —C₂H₄CF₂O—, —C₂H₄OCF₂—, —CF₂OC₂H₄—, or—OCF₂C₂H₄—. Z¹ is preferably a single bond, —CH₂O—, or —(CH₂)₂—. When Z¹is —CH₂O—, the formula (1) is not R¹-A¹-OCH₂-A²-Z²-(A³)_(n)-R², butR¹-A¹-CH₂O-A²-Z²-(A³)_(n)-R². This rule is applicable to Z², Z³, Z⁴, Z⁵,and Z⁶. Z³ is a single bond or —COO—, preferably a single bond. Z⁴ is asingle bond, —CH₂O—, or —OCH₂—, preferably a single bond or —CH₂O—. Z⁵is —(CH₂)₂——or —(CH₂)₄—, preferably —(CH₂)₂—. Z⁶ is —CF₂O—, —OCF₂—,—C₂H₄CF₂O—, —C₂H₄OCF₂—, —CF₂OC₂H₄—, or —OCF₂C₂H₄—, preferably—OCF₂C₂H₄—, —C₂H₄CF₂O—, or —CF₂O—.

Fifth, concrete examples of the component compounds will be shown.Preferred compounds (1-1) include compounds (1-1-1) to (1-1-10).Preferred compounds (1-2) include compounds (1-2-1) to (1-2-6).Preferred compounds (1-3) include compounds (1-3-1) to (1-3-18).Preferred compounds (1-4) include compounds (1-4-1) to (1-4-9).Preferred compounds (1-5) include compounds (1-5-1) to (1-5-6).Preferred compounds (1-6) include compounds (1-6-1) to (1-6-18).Preferred compounds (1-7) include compounds (1-7-1) to (1-7-6).Preferred compounds (1-8) include compounds (1-8-1) to (1-8-6).Preferred compounds (1-9) include compounds (1-9-1) to (1-9-18).Preferred compounds (1-10) include compounds (1-10-1) to (1-10-4).Preferred compounds (1-11) include compounds (1-11-1) to (1-11-4).Preferred compounds (1-12) include compounds (1-12-1) to (1-12-12). Morepreferred compounds (1) include compounds (1-1-1) to (1-1-10), (1-3-1)to (1-3-18), (1-4-1) to (1-4-9), (1-6-1) to (1-6-18), (1-7-1) to(1-7-6), (1-9-1) to (1-9-18), (1-10-1) to (1-10-4), and (1-12-1) to(1-12-12). Particularly preferred compounds (1) include compounds(1-1-1), (1-4-1), and (1-7-1).

Preferred compounds (2-1) include compounds (2-1-1) to (2-1-5).Preferred compounds (2-2) include compounds (2-2-1) to (2-2-2).Preferred compounds (2-3) include compounds (2-3-1) to (2-3-4). Morepreferred compounds (2) include compounds (2-1-1) to (2-1-5), (2-2-1),(2-2-2), and (2-3-1) to (2-3-4). Particularly preferred compounds (2)include compounds (2-1-1), (2-1-4), (2-2-1), and (2-3-1).

Preferred compounds (3-1) include compounds (3-1-1) to (3-1-2).Preferred compounds (3-2) include compounds (3-2-1) to (3-2-4).Preferred compounds (3-3) include compounds (3-3-1) to (3-3-3).Preferred compounds (3-4) include compounds (3-4-1) to (3-4-2). Morepreferred compounds (3) include compounds (3-1-1), (3-1-2), (3-2-1) to(3-2-4), (3-3-1) to (3-3-3), (3-4-1), and (3-4-2).

Preferred compounds (4) include compounds (4-1) to (4-28). In theexemplified compounds and the preferred compounds, the groups R¹'s, etc.may be the same or different ones as described above.

R¹ is alkyl or alkenyl, preferably alkyl having 1 to 10 carbon atoms oralkenyl having 2 to 10 carbon atoms. R² is alkyl, alkenyl, or alkoxy,preferably alkyl having 1 to 10 carbon atoms, alkenyl having 2 to 10carbon atoms, or alkoxy having 1 to 10 carbon atoms. R⁴ is alkyl,preferably alkyl having 1 to 10 carbon atoms. R⁵ is alkyl, alkenyl,alkoxy, or alkoxymethyl, preferably alkyl having 1 to 10 carbon atoms,alkenyl having 2 to 10 carbon atoms, alkoxy having 1 to 10 carbon atoms,or alkoxymethyl having 2 to 10 carbon atoms. One of Y¹ and Y² isfluorine, and the other is —CF₂H. Y³ and Y⁴ are independently hydrogen,fluorine, or —CF₂H, and at least one of Y³ and Y⁴ is not —CF₂H. Y⁵ andY⁶ are independently hydrogen or fluorine. Preferred alkyl, alkenyl,alkoxy, and alkoxymethyl, and more preferred alkyl, alkenyl, alkoxy, andalkoxymethyl are as described above. Preferred —CH═CH— configuration ofthe alkenyl is as described above. In the 1,4-cyclohexylene of thesepreferable compounds, trans configuration is preferable to cisconfiguration.

Sixth, the synthesis methods of the component compounds will beexplained. The compounds can be synthesized by known methods. Thesynthesis methods will be exemplified. The compound (1) may besynthesized by modifying methods described in WO 2000-39063 A. Thecompound (2-1-1) may be synthesized by methods described inJP-A-59-70624 and JP-A-60-16940. The compound (4) may be synthesized bymodifying methods described in JP-A-6-228037.

The compounds where their synthesis methods were not described above maybe synthesized according to methods described in Organic Synthesis (JohnWiley & Sons, Inc.), Organic Reactions (John Wiley & Sons, Inc.),Comprehensive Organic Synthesis (Pergamon Press), Shin Jikken KagakuKouza (New Experimental Chemistry Course, Maruzen, Inc.), and so forth.The composition is prepared from thus-obtained compounds according toknown methods. For example, the component compounds are mixed anddissolved in each other by heating to prepare the composition.

The composition of the invention generally has an optical anisotropy of0.05 to 0.11 and a dielectric anisotropy of −6.5 to −2.0. The dielectricanisotropy is preferably within the range of −5.0to −2.5. By controllingthe ratio of the component compounds or by mixing another compound, acomposition having an optical anisotropy of 0.05 to 0.18 may beprepared, and further a composition having an optical anisotropy of 0.05to 0.20 may be prepared. Thus, the composition is suitable for an AMelement of a VA mode, an IPS mode, etc., and particularly suitable foran AM element of a VA mode.

In elements of a TN mode, a VA mode, etc., the electric field directionis perpendicular to the normal direction of a substrate. In elements ofan IPS mode, etc., the electric field direction is parallel to thenormal direction of a substrate. A structure of an element having a VAmode has been reported in K. Ohmuro, S. Kataoka, T. Sasaki, and Y.Koike, SID 97 Digest of Technical Papers, 28, 845 (1997). A structure ofan element having an IPS mode has been reported in WO 1991-10936 A (U.S.Pat. No. 5,576,867). The composition of the invention is suitable alsofor these elements.

The composition can be used not only for an AM element but also for a PMelement. The composition can be used for elements having a PC, TN, STN,or OCB mode, and so forth. These elements may be a reflection type, atransmission type, or a semi-transmission type. The composition is alsousable for a nematic curvilinear aligned phase (NCAP) element producedby microencapsulation, and for a polymer dispersed (PD) element such asa polymer network (PN) element, which has a three-dimensional polymernetwork in the composition.

EXAMPLES

The present invention will be explained in detail with reference toExamples without intention of restricting the scope of the invention.Compounds used in Examples are expressed by symbols according todefinition shown in Table 8. In Table 8, 1,4-cyclohexylene has transconfiguration. In Examples, parenthesized numbers next to the symbolscorrespond to the numbers of the preferred compounds. The symbol (−)means another compound. The content (percentage) of each compound isshown in percentage by weight (% by weight) based on the total weight ofthe composition. Finally the characteristics of the composition aresummarized. TABLE 8 Method for Description of Compounds using symbolsR—(A₁)—Z₁—. . .—Z_(n)-(A_(n))—X Symbol 1) Left terminal group R—C_(n)H_(2n+1)— n- CH₂═CH— V- C_(n)H_(2n+1)CH═CH— nV- 2) Ring structure—(A_(n))—

B

B(3F)

B(2F)

B(2F,3F)

B(2CF₂H,3F)

B(2F,3CF₂H)

H 3) Bonding group —Z_(n)— —COO— E —CF₂O— CF₂O —OCF₂ OCF₂ —CF₂OC₂H_(4—)CF₂O2 —OCF₂C₂H₄— OCF₂2 5)Example of Description Example 1.3-HH1OB(2CF₂H,3F)—O2

Example 2. 3-HHB(2F,3CF₂H)—O2

Example 3. 3-HBB(2F)—O2

The composition is prepared by measuring the weights of components suchas liquid crystalline compounds, and then mixing the components. Thus,the content (% by weight) of each component can be easily calculated. Itis not easy to precisely calculate the content of each component by gaschromatograph analysis of the composition, because correction factordepend on the type of the liquid crystalline compound. In the invention,fortunately the correction factors are approximately 1. Further,difference of 1% by weight between the component compounds has only asmall effect on the characteristics of the composition. Thus, in theinvention, the area ratio of each component peak obtained in the gaschromatograph can be considered as the content (% by weight) of thecomponent. Accordingly, the results of the gas chromatograph analysis(the area ratios of the peaks) may be regarded as being equivalent tothe contents of the components without correction.

When a sample was a composition, it was measured without modification,and the value was described. When a sample was a compound, 15% by weightof the compound was mixed with 85% by weight of a liquid crystal matrixand then subjected to the measurement. The characteristic values of thecompound were calculated from the measured values by an extrapolationmethod using an extrapolation value of (measured value of sample−0.85×measured value of liquid crystal matrix)/0.15. When a smecticphase (or a crystal) was generated at this mixing ratio at 25° C., themixing ratio of the compound to the liquid crystal matrix was changed to10:90, 5:95, and 1:99% by weight, in this order. The higher limittemperature, the optical anisotropy, the viscosity, and the dielectricanisotropy of the compound were obtained by the extrapolation method.

The liquid crystal matrix had the following composition.

Characteristic values were measured by the methods to be describedbelow. Most of the methods are those described in EIAJ ED-2521A ofStandard of Electric Industries Association of Japan or modificationthereof. TN elements used in the measurement were not equipped with aTFT.

Higher limit temperature of nematic phase temperature range (NI; ° C.):A sample was placed on a hot plate of a melting point apparatus equippedwith a polarizing microscope, and was heated at the rate of 1° C./minuteto measure a temperature, at which a part of the sample began to changefrom the nematic phase into an isotropic liquid. The higher limittemperature of the nematic phase temperature range may be abbreviated to“the higher limit temperature.”

Lower limit temperature of nematic phase temperature range (T_(C); °C.): A sample having a nematic phase was put in a glass bottle andstored in a freezer at 0° C., −10° C., −20° C., −30° C., or −40° C. for10 days, and the liquid crystal phase was observed. For example, whenthe sample maintained the nematic phase at −20° C. and changed to acrystal or smectic phase at −30° C., the lower limit temperature of thenematic phase was expressed as T_(C)≦−20° C. The lower limit temperatureof the nematic phase temperature range may be abbreviated to “the lowerlimit temperature.”

Viscosity (η; at 20° C.; mPa.s): An E-type rotational viscometer wasused in the measurement.

Rotational viscosity (γ1; at 25° C.; mPa.s) : A rotational viscosity wasmeasured according to a method described in M. Imai, et al., MolecularCrystals and Liquid Crystals, Vol. 259, 37 (1995). A sample wasintroduced into a VA element having two glass plates at an interval(cell gap) of 20 μm. A voltage of 30 to 50 V was applied to the elementwhile changing the voltage stepwise by 1 V. The element was left underno applied voltage for 0.2 seconds, and then the voltage application wasrepeated such that only one rectangular wave (rectangular pulse) wasapplied for 0.2 seconds and no voltage was applied for 2 seconds. Atransient current generated by the application was measured with respectto the peak current and the peak time. The rotational viscosity of thesample was calculated from the measured values by a computationalexpression (8) described in M. Imai, et al., ibid., Page 40. Adielectric anisotropy measured by the following method was used for thecalculation.

Optical anisotropy (refractive anisotropy; Δn; at 25° C.): A light witha wavelength of 589 nm, and an Abbe refractometer having an eyepieceequipped with a polarizing plate were used in the measurement. A surfaceof the main prism was rubbed in one direction, and then a sample was puton the main prism dropwise. A refractive index n∥ was measured when thepolarization direction was parallel to the rubbing direction. Arefractive index n⊥ was measured when the polarization direction wasperpendicular to the rubbing direction. The optical anisotropy of thesample was calculated using the equation of Δn=n∥−n⊥.

Dielectric anisotropy (Δε; at 25° C.): A sample was introduced into a VAelement having two glass plates at an interval (cell gap) of 20 μm. Asine wave (0.5 V, 1 kHz) was applied to the element, and a dielectricconstant (ε∥) in the longitudinal direction of the liquid crystalmolecules was measured 2 seconds after the beginning of the application.A sample was introduced into a TN element, which had two glass plates atan interval (cell gap) of 9 μm, and had a twist angle of 80 degrees. Asine wave (0.5 V, 1 kHz) was applied to the element, and a dielectricconstant (ε⊥) in the lateral direction of the liquid crystal moleculeswas measured 2 seconds after the beginning of the application. Thedielectric anisotropy was calculated using the equation of Δε=ε∥−ε⊥.

Threshold voltage (Vth; at 25° C.; V): LCD5100 luminance metermanufactured by Otsuka Electronics Co., Ltd. was used in themeasurement. A halogen lamp was used as a light source. A sample wasintroduced into a TN element of a normally white mode, which had twoglass plates at an interval (cell gap) of 5.0 μm, and had a twist angleof 80 degrees. A voltage (32 Hz, rectangular wave) was applied to theelement while increasing the voltage from 0 V to 10 V stepwise by 0.02V. The element was irradiated with a light from the vertical direction,and the quantity of the light transmitted through the element wasmeasured. The transmittance was considered as 100% when the lightquantity was the maximum value, the transmittance was considered as 0%when the light quantity was the minimum value, and thus avoltage-transmittance curve was obtained. The threshold voltage is avoltage at which the transmittance was 90%.

Voltage holding ratio (VHR; at 25° C. and 100° C.; %) : A TN elementused for the measurement had a polyimide alignment film and had twoglass plates at an interval (cell gap) of 6 μm. A sample was introducedinto the element, and the element was sealed with an ultravioletpolymerization type adhesive. A pulse voltage (5V, 60 microseconds) wasapplied to the TN element to charge the element. The voltage decay wasmeasured for 16.7 milliseconds by a fast voltmeter, to obtain an area Abetween a voltage curve and a horizontal axis in a unit period. Also anarea B was obtained when the voltage was not decayed. A voltage holdingratio is the percentage of the area A to the area B. A voltage holdingratio measured at 25° C. was expressed as VHR-1, and a voltage holdingratio measured at 100° C. was expressed as VHR-2. Then, the TN elementwas heated at 100° C. for 250 hours. A voltage holding ratio of theheated element measured at 25° C. was expressed as VHR-3, and a voltageholding ratio of the heated element measured at 100° C. was expressed asVHR-4. VHR-1 and VHR-2 corresponded to initial characteristics, andVHR-3 and VHR-4 corresponded to characteristics shown after the elementhad been used for a long time.

Response time (T; at 25° C.; millisecond): LCD5100 luminance metermanufactured by Otsuka Electronics Co., Ltd. was used in themeasurement. A halogen lamp was used as a light source, and a low-passfilter was set at 5 kHz. A sample was introduced into a TN element of anormally white mode, which had two glass plates at an interval (cellgap) of 5.0 μm, and had a twist angle of 80 degrees. A rectangular wave(60 Hz, 5 V, 0.5 seconds) was applied to the element. The element wasirradiated with a light from the vertical direction, and the quantity ofthe light transmitted through the element was measured. Thetransmittance was considered as 100% when the light quantity was themaximum value, and the transmittance was considered as 0% when the lightquantity was the minimum value. A rise time (τr) was obtained as a timerequired for changing the transmittance from 90% to 10%, and a fall time(τf) was obtained as a time required for changing the transmittance from10% to 90%. A response time is the sum of thus-obtained rise time andfall time.

Gas chromatograph analysis: GC-14B gas chromatograph manufactured byShimadzu Corporation was used in the measurement. Helium was used at therate of 2 ml/minute as a carrier gas. The temperature of a samplevaporizing chamber was set at 280° C., and the temperature of a detector(FID) was set at 300° C. Capillary column DB-1 available from AgilentTechnologies Inc. (length 30 m, inner diameter 0.32 mm, film thickness0.25 μm, dimethylpolysiloxane stationary liquid phase, nonpolar) wasused for separating component compounds. The column was kept at 200° C.for 2 minutes, and then heated to 280° C. at the rate of 5° C./minute. Asample was prepared in the form of a 0.1% by weight acetone solution,and 1 μl thereof was introduced into the sample vaporizing chamber. Usedas a recorder was C-R5A Chromatopac manufactured by Shimadzu Corporationor an equivalent thereof. The obtained gas chromatogram showed theretention times and the areas of peaks corresponding to the componentcompounds.

Chloroform, hexane, and so forth may be used as a solvent for dilutingthe sample. The component compounds may be separated by using acapillary column such as HP-1 available from Agilent Technologies Inc.(length 30 m, inner diameter 0.32 mm, film thickness 0.25 μm), Rtx-1available from Restek Corporation (length 30 m, inner diameter 0.32 mm,film thickness 0.25 μm), and BP-1 available from SGE International Pty.Ltd. (length 30 m, inner diameter 0.32 mm, film thickness 0.25 μm). Acapillary column CBP1-M50-025 available from Shimadzu Corporation(length 50 m, inner diameter 0.25 mm, film thickness 0.25 μm) may beused to prevent overlapping of the compound peaks. The area ratio of thepeaks in the gas chromatogram corresponds to the ratio of the componentcompounds. The content (% by weight) of each component compound is notcompletely equal to the area ratio of each peak. However, when the abovecapillary columns are used in the invention, the content of thecomponent compound can be regarded as being equal to the area ratio ofthe peak because the correction factors of the component compounds haveno great differences.

Example 1

3-HB(2F,3CF₂H)—O2 (1-1-1)  3% 5-HB(2F,3CF₂H)—O2 (1-1-1)  3%2-HH1OB(2CF₂H,3F)—O2 (1-7-1) 12% 3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 12%5-HH1OB(2CF₂H,3F)—O2 (1-7-1) 12% 2-HH-5 (2-1-1)  8% 3-HH-4 (2-1-1) 10%3-HH-5 (2-1-1) 10% 3-HB—O2 (2-1-4) 10% 5-HB—O2 (2-1-4) 10% 3-HHB-1(2-2-1) 10%

NI=70.7° C.; Tc<−20° C.; Δn=0.071; Δε=−3.9; η=38.4 mPa.s.

Example 2

2-HHB(2F,3CF₂H)—O2 (1-4-1) 5% 3-HHB(2F,3CF₂H)—O2 (1-4-1) 8%5-HHB(2F,3CF₂H)—O2 (1-4-1) 8% 3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10% 5-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10%  3-HH—V (2-1-1) 10%  5-HH—V (2-1-1)25%  3-HH—V1 (2-1-1) 5% 3-HB—O1 (2-1-4) 7% 3-HB—O2 (2-1-4) 7% 3-HBBH-4(2-3-2) 5%

NI=74.0° C.; Tc<−20° C.; Δn=0.066; Δε=−3.5; η=35.2 mPa.s.

Example 3

5-HB(2F,3CF₂H)—O2 (1-1-1) 5% 5-HB(2F,3CF₂H)—O4 (1-1-1) 3%2-HHB(2F,3CF₂H)—O2 (1-4-1) 10%  3-HHB(2F,3CF₂H)—O2 (1-4-1) 12% 5-HHB(2F,3CF₂H)—O2 (1-4-1) 12%  5-HH—V (2-1-1) 24%  3-HH—V1 (2-1-1) 5%3-HB—O2 (2-1-4) 6% V-HHB-1 (2-2-1) 10%  V2-HHB-1 (2-2-1) 8% 3-HBBH-1O1(2-3-2) 5%

NI=85.1° C.; Tc<−20° C.; Δn=0.074; Δε=−3.4; η=42.1 mPa.s.

Example 4

3-HHB(2F,3CF₂H)—O2 (1-4-1) 10% 5-HHB(2F,3CF₂H)—O2 (1-4-1) 10%2-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10% 3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10% 3-HH—V(2-1-1) 12% 5-HH—V (2-1-1) 25% 3-HH—V1 (2-1-1)  5% 3-HHB(2F,3F)—O2(4-24) 10% 3-HBB(2F,3F)—O2 (4-25)  8%

NI=85.4° C.; Tc<−20° C.; Δn=0.068; Δε=−4.6; η=39.91 mPa.s.

Example 5

2-HH1OB(2CF₂H,3F)—O2 (1-7-1)  5% 3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10%5-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10% 3-HH-4 (2-1-1)  7% 5-HB-3 (2-1-4)  3%7-HB-1 (2-1-4)  5% 3-HHB-1 (2-2-1) 10% 3-HHB-3 (2-2-1) 10% 3-HHB—O1(2-2-1) 10% 3-HB(2F,3F)—O2 (4-23)  5% 3-HB(2F,3F)—O4 (4-23)  5%5-HB(2F,3F)—O2 (4-23) 10% 5-HB(2F,3F)—O4 (4-23) 10%

NI=80.2° C.; Tc<−20° C.; Δn=0.079; Δε=−3.7; η=37.1 mPa.s; VHR-1=99.2%.

Example 6

3-HHB(2F,3CF₂H)—O2 (1-4-1) 7% 5-HHB(2F,3CF₂H)—O2 (1-4-1) 7% 2-HH-5(2-1-1) 5% 3-HH-4 (2-1-1) 15%  3-HH-5 (2-1-1) 8% 3-HHB-1 (2-2-1) 5%3-HHB-3 (2-2-1) 5% 3-HHB—O1 (2-2-1) 3% 3-HBBH-4 (2-3-2) 5%3-HB(2F,3F)—O2 (4-23) 10%  3-HB(2F,3F)—O4 (4-23) 10%  3-HHB(2F,3F)—O2(4-24) 5% 3-HBB(2F,3F)—O2 (4-25) 5% 3-HB(3F)B(2F,3F)—O2 (4-26) 5%3-HB(2F)B(2F,3F)—O2 (4-27) 5%

NI=90.9° C.; Tc<−20° C.; Δn=0.083; Δε=−3.9; η=32.5 mPa.s.

Example 7

2-HH1OB(2CF₂H,3F)—O2 (1-7-1) 8% 3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 8%5-HH1OB(2CF₂H,3F)—O2 (1-7-1) 8% 3-HB(2F)-3 (3-1-1) 7% 3-HB(2F)—O2(3-1-1) 7% 3-HB(3F)-3 (3-1-2) 7% 3-HB(3F)—O2 (3-1-2) 7% 3-H1OB(2F)-3(3-3-1) 5% 3-H1OB(2F)—O2 (3-3-1) 5% 3-H1OB(2F)H-3 (3-3-2) 7%3-H1OB(2F)H—O2 (3-3-2) 7% 3-H1OB(2F)B-3 (3-3-3) 7% 3-H1OB(2F)B—O2(3-3-3) 7% 3-HH1OB(2F)—O2 (3-4-1) 5% 3-HH1OB(2F)-1 (3-4-1) 5%

NI=70.1° C.; Tc<−20° C.; Δn=0.098; Δε=−4.0; η=43.3 mPa.s; VHR-1=99.6%.

Example 8

3-HB(2F,3CF₂H)—O4 (1-1-1) 5% 3-HHB(2F,3CF₂H)—O2 (1-4-1) 5%5-HHB(2F,3CF₂H)—O2 (1-4-1) 5% 2-HH1OB(2CF₂H,3F)—O2 (1-7-1) 3%3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10%  5-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10% 3-HB(2F)-3 (3-1-1) 10%  3-HB(3F)-3 (3-1-2) 7% 3-HB(3F)—O2 (3-1-2) 8%3-HHB(2F)—O2 (3-2-1) 5% 3-HHB(2F)-1 (3-2-1) 5% 3-HHB(3F)—O2 (3-2-2) 7%3-HHB(3F)-1 (3-2-2) 5% 3-H1OB(2F)H—O2 (3-3-2) 5% 3-H1OB(2F)B—O2 (3-3-3)5% 3-HH1OB(2F)—O2 (3-4-1) 5%

NI=81.2° C.; Δn=0.089; Δε=−4.8; η=49.7 mPa.s.

Example 9

5-HHB(2F,3CF₂H)—O2 (1-4-1) 4% 2-HH1OB(2CF₂H,3F)—O2 (1-7-1) 3%3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10%  5-HH1OB(2CF₂H,3F)—O2 (1-7-1) 10% 3-HB(2F)—O2 (3-1-1) 9% 3-HB(3F)—O2 (3-1-2) 9% 3-HHB(2F)-1 (3-2-1) 8%3-HHB(3F)—O2 (3-2-2) 6% 3-HHB(3F)-1 (3-2-2) 6% 3-HBB(2F)—O2 (3-2-3) 6%3-HBB(2F)-1 (3-2-3) 5% 5-HB(2F,3F)—O2 (4-23) 8% 5-HB(2F,3F)—O4 (4-23) 8%3-HBB(2F,3F)—O2 (4-25) 8%

NI=86.7° C.; Δn=0.099; Δε=−4.9; η=43.9 mPa.s.

Example 10

3-HH1OB(2CF₂H,3F)—O2 (1-7-1) 8% 5-HH1OB(2CF₂H,3F)—O2 (1-7-1) 8%3-H1OB(2F)-3 (3-3-1) 6% 3-H1OB(2F)—O2 (3-3-1) 7% 3-H1OB(2F)H-3 (3-3-2)7% 3-H1OB(2F)H—O2 (3-3-2) 7% 3-HH1OB(2F)—O2 (3-4-1) 5% 3-HH1OB(2F)-1(3-4-1) 5% 3-HB1OB(2F)—O2 (3-4-2) 5% 3-HB1OB(2F)-1 (3-4-2) 5%3-HB(2F,3F)—O2 (4-23) 5% 3-HB(2F,3F)—O4 (4-23) 5% 5-HB(2F,3F)—O2 (4-23)6% 5-HB(2F,3F)—O4 (4-23) 6% 3-HHB(2F,3F)—O2 (4-24) 10%  3-HBB(2F,3F)—O2(4-25) 5%

NI=79.8° C.; Δn=0.093; Δε=−4.3; η=41.7 mPa.s.

Example 11

5-HB(2F,3CF₂H)—O2 (1-1-1) 5% 5-HB(2F,3CF₂H)—O4 (1-1-1) 3%2-HHB(2F,3CF₂H)—O2 (1-4-1) 10%  3-HHB(2F,3CF₂H)—O2 (1-4-1) 12% 5-HHB(2F,3CF₂H)—O2 (1-4-1) 12%  5-HH—V (2-1-1) 24%  3-HH—V1 (2-1-1) 5%3-HB—O2 (2-1-4) 6% V-HHB-1 (2-2-1) 10%  V2-HHB-1 (2-2-1) 8% 1O1-HBBH—O1(−) 5%

NI=86.6° C.; Tc<−20° C.; Δn=0.074; Δε=−3.4; η=42.6 mPa.s.

1. A liquid crystal composition with a negative dielectric anisotropy,comprising at least one compound selected from the group of compoundsrepresented by the following formula (1) as a first component, and atleast one compound selected from the group of compounds represented bythe following formulas (2-1) to (2-3) and (3-1) to (3-4) as a secondcomponent:

wherein R¹ is alkyl or alkenyl; R² is alkyl, alkenyl, or alkoxy; R³ isalkyl, alkenyl, alkoxy, or —COO—R⁴, in which R⁴ is alkyl; R⁵ is alkyl,alkenyl, alkoxy, or alkoxymethyl; Z¹ and Z² are independently a singlebond, —CH₂O—, —OCH₂—, —(CH₂)₂—, —(CH₂)₄—, —CF₂O—, —OCF₂—, —C₂H₄CF₂O—,—C₂H₄OCF₂—, —CF₂OC₂H₄—, or —OCF₂C₂H₄—; Z³ is a single bond or —COO—; A¹is 1,4-cyclohexylene or 1,4-phenylene; A² and A³ are independently1,4-cyclohexylene, 1,4-phenylene, 1,4-phenylene in which any hydrogenmay be replaced by fluorine, or 2-difluoromethyl-3-fluoro-1,4-phenylene;A⁴ is 1,4-cyclohexylene, 1,4-phenylene, or 1,4-phenylene in which ahydrogen is replaced by a fluorine; A⁵ is 1,4-phenylene or 1,4-phenylenein which a hydrogen is replaced by a fluorine; A⁶is2-fluoro-1,4-phenylene; n is 0 or 1; in the formula (1), when n is 0, A²is 2-difluoromethyl-3-fluoro-1,4-phenylene, and Z² is a single bond; andin the formula (1), when n is 1, one of A² and A³ is2-difluoromethyl-3-fluoro-1,4-phenylene, and one of Z¹ and Z² is asingle bond.
 2. The liquid crystal composition according to claim 1,wherein, in the formula (1), Z¹ is a single bond, A¹ is1,4-cyclohexylene, A² is 2-difluoromethyl-3-fluoro-1,4-phenylene, and nis
 0. 3. The liquid crystal composition according to claim 1, wherein,in the formula (1), Z¹ is a single bond or —CH₂O—, A¹ and A² are1,4-cyclohexylene, and A³ is 2-difluoromethyl-3-fluoro-1,4-phenylene. 4.The liquid crystal composition according to claim 1, wherein the firstcomponent is at least one compound selected from the group of compoundsrepresented by the following formulas (1-1) to (1-12):R¹-A¹-Z⁴-A⁷-(A⁸)_(n)-R²   (1-1)R¹-A¹-Z⁵-A⁷-(A⁸)_(n)-R²   (1-2)R¹-A¹-Z⁶-A⁷-(A⁸)_(n)-R²   (1-3)R¹-A¹-Z⁴-A⁸-A⁷-R²   (1-4)R¹-A¹-Z⁵-A⁸-A⁷-R²   (1-5)R¹-A¹-Z⁶-A⁸-A⁷-R²   (1-6)R¹-A¹-A⁸-Z⁴-A⁷-R²   (1-7)R¹-A¹-A⁸-Z⁵-A⁷-R²   (1-8)R¹-A¹-A⁸-Z⁶-A⁷-R²   (1-9)R¹-A¹-A⁷-Z⁴-A⁸-R²   (1-10)R¹-A¹-A⁷-Z⁵-A⁸-R²   (1-11)R¹-A¹-A⁷-Z⁶-A⁸-R²   (1-12) wherein R¹ is alkyl or alkenyl; R² is alkyl,alkenyl, or alkoxy; Z⁴ is a single bond, —CH₂O—, or —OCH₂—; Z⁵ is—(CH₂)₂— or —(CH₂)₄—; Z⁶ is —CF₂O—, —OCF₂—, —C₂H₄CF₂O—, —C₂H₄OCF₂—,—CF₂OC₂H₄—, or —OCF₂C₂H₄—; A¹ is 1,4-cyclohexylene or 1,4-phenylene; A⁷is 1,4-phenylene in which a hydrogen is replaced by a fluorine, or2-difluoromethyl-3-fluoro-1,4-phenylene; A⁸ is 1,4-cyclohexylene,1,4-phenylene, 1,4-phenylene in which a hydrogen is replaced by afluorine, or 2-difluoromethyl-3-fluoro-1,4-phenylene; one of A⁷ and A⁸is 2-difluoromethyl-3-fluoro-1,4-phenylene; n is 0 or 1; and in theformulas (1-1) to (1-3), when n is 0, A⁷ is2-difluoromethyl-3-fluoro-1,4-phenylene.
 5. The liquid crystalcomposition according to claim 4, wherein the first component is atleast one compound selected from the group of the compounds representedby the formulas (1-1), (1-3), (1-4), (1-6), (1-7), (1-9), (1-10), and(1-12).
 6. The liquid crystal composition according to claim 4, wherein,in the formula (1-1), Z⁴ is a single bond, A¹ is 1,4-cyclohexylene, A⁷is 2-difluoromethyl-3-fluoro-1,4-phenylene, and n is
 0. 7. The liquidcrystal composition according to claim 4, wherein, in the formulas(1-4), (1-7), and (1-10), Z⁴ is a single bond or —CH₂O—, A¹ and A⁸ are1,4-cyclohexylene, and A⁷ is 2-difluoromethyl-3-fluoro-1,4-phenylene. 8.The liquid crystal composition according to claim 2, wherein the secondcomponent is at least one compound selected from the group of thecompounds represented by the formulas (2-1) to (2-3).
 9. The liquidcrystal composition according to claim 3, wherein the second componentis at least one compound selected from the group of the compoundsrepresented by the formulas (2-1) to (2-3).
 10. The liquid crystalcomposition according to claim 2, wherein the second component is atleast one compound selected from the group of the compounds representedby the formula (2-1).
 11. The liquid crystal composition according toclaim 3, wherein the second component is at least one compound selectedfrom the group of the compounds represented by the formula (2-1). 12.The liquid crystal composition according to claim 2, wherein the secondcomponent is at least one compound selected from the group of thecompounds represented by the formula (2-2).
 13. The liquid crystalcomposition according to claim 3, wherein the second component is atleast one compound selected from the group of the compounds representedby the formula (2-2).
 14. The liquid crystal composition according toclaim 3, wherein the second component is at least one compound selectedfrom the group of the compounds represented by the formula (2-3). 15.The liquid crystal composition according to claim 3, wherein the secondcomponent is at least one compound selected from the group of thecompounds represented by the formulas (3-1) to (3-4).
 16. The liquidcrystal composition according to claim 3, wherein the second componentis at least one compound selected from the group of compoundsrepresented by the following formulas (2-1-1), (2-1-2), (2-1-3),(2-1-4), (2-1-5), (2-2-1), (2-2-2), (2-3-1), (2-3-2), (2-3-3), and(2-3-4):

wherein R¹ is alkyl or alkenyl; R² is alkyl, alkenyl, or alkoxy; R⁴isalkyl; and R⁵ is alkyl, alkenyl, alkoxy, or alkoxymethyl.
 17. The liquidcrystal composition according to claim 16, wherein the second componentis a compound selected from the group of the compounds represented bythe formulas (2-1-1), (2-1-4), (2-2-1), and (2-3-1).
 18. The liquidcrystal composition according to claim 3, wherein the liquid crystalcomposition comprises 5 to 90% by weight of the first component and 5 to90% by weight of the second component based on the total weight of thecomposition.
 19. The liquid crystal composition according to claim 17,wherein the liquid crystal composition comprises 5 to 90% by weight ofthe first component and 5 to 90% by weight of the second component basedon the total weight of the composition.
 20. The liquid crystalcomposition according to claim 3, further comprising at least onecompound selected from the group of compounds represented by thefollowing formula (4) as a third component:

wherein R¹ is alkyl or alkenyl; R² is alkyl, alkenyl, or alkoxy; Z⁴ andZ⁵ are independently —CF₂O— or —OCF₂—; A⁴ is 1,4-cyclohexylene,1,4-phenylene, or 1,4-phenylene in which a hydrogen is replaced by afluorine; and n is 0 or
 1. 21. The liquid crystal composition accordingto claim 17, further comprising at least one compound selected from thegroup of compounds represented by the following formula (4) as a thirdcomponent:

wherein R¹ is alkyl or alkenyl; R²is alkyl, alkenyl, or alkoxy; Z⁴ andZ⁵ are independently —CF₂O— or —OCF₂—; A⁴ is 1,4-cyclohexylene,1,4-phenylene, or 1,4-phenylene in which a hydrogen is replaced by afluorine; and n is 0 or
 1. 22. The liquid crystal composition accordingto claim 20, wherein the liquid crystal composition comprises 2 to 50%by weight of the third component based on the total weight of thecomposition.
 23. The liquid crystal composition according to claim 21,wherein the liquid crystal composition comprises 2 to 50% by weight ofthe third component based on the total weight of the composition. 24.The liquid crystal composition according to claim 3, wherein the liquidcrystal composition has a dielectric anisotropy of −6.5 to −2.0.
 25. Aliquid crystal display element comprising the liquid crystal compositionaccording to claim
 3. 26. A liquid crystal display element comprisingthe liquid crystal composition according to claim
 17. 27. The liquidcrystal display element according to claim 25, wherein the liquidcrystal display element uses a VA or IPS mode, and is driven by anactive matrix.
 28. The liquid crystal display element according to claim26, wherein the liquid crystal display element uses a VA or IPS mode,and is driven by an active matrix.
 29. A method of using the liquidcrystal composition according to claim 3 for a liquid crystal displayelement that uses a VA or IPS mode and is driven by an active matrix.30. A method of using the liquid crystal composition according to claim17 for a liquid crystal display element that uses a VA or IPS mode andis driven by an active matrix.